Late Cenozoic geomorphic evolution in response to inversion: Evidence from field and GPR studies in Kim drainage basin, western India

This study presents field and ground penetrating radar (GPR) data for understanding geomorphic evolution of the Kim-drainage basin in response to tectonic inversion of the Narmada–Ankleshwar block of the Cambay rift basin located on the western-continental margin of India. The Narmada–Ankleshwar block underwent continuous sedimentation up to Mio–Pliocene and subsequently was subjected to compressional inversion. Four geomorphic surfaces are recognised that formed in response to the varying degrees of tectonic activity related to phases of inversion. These are the early Pleistocene erosional surface (EPES), late Pleistocene depositional surface (LPDS), early Holocene erosional surface (EHES) and the late Holocene depositional surface (LHDS). The phases of increased tectonic activity relate to two erosional episodes, while two depositional periods relate to waning tectonic activity or quiescent periods. We show that the Narmada–Ankleshwar block suffered inversion earlier than other parts of the Cambay basin to the north of the NSF. Localisation of early inversion movements occurred in an area characterised by thinner crust and involved the development of new reverse faults and transformation of the NSF from a normal to a reverse fault. GPR studies indicate the reverse nature of the various faults in the Kim drainage basin and provide evidence of their late reactivation under compression. The study demonstrates that the parts of a large sedimentary basin can undergo inversion at different times depending on the orientation of pre-existing crustal discontinuities with respect to the controlling stress trajectories.